Multiaxis NC machine tools, having at least one rotational axis of A-, B- and C-axes in addition to three orthogonal feed axes of X-, Y- and Z-axes, are widely used. In such a multiaxis NC machine tool, a spindle side structure and a table side structure are moved relative to each other in the directions of the liner feed axes of X-, Y- and Z-axes and the rotations feed axes of A-, B- and C-axes. A workpiece, attached to a table, is processed with a tool attached to a spindle. A measuring prove may be attached to measure the size of a workpiece. A manual operation mode, for manually moving a feed axis with a jog feeding operation or a handle feeding operation without using an NC program, is well known in the art.
Although there are configurations in which all of the feed axes of the orthogonal linear feed axes and the rotation feed axes are provided in a spindle side structure or in a table side structure, in most machine tools, part of the feed axes are provided in the spindle side structure and the other of the feed axes are provide in the table side structure. Accordingly, there are a various types of machine tools from the point of view of the arrangement of the feed axes. For example, regarding the X-axis, in a machine tool in which the table side structure moves in the left-right direction viewing from an operator, the direction in which the table side structure moves to the left is defined as the positive (+) direction of the X-axis, while in a machine tool in which the spindle side structure moves in the left-right direction, the direction in which the table side structure moves to the right is defined as the positive (+) direction of the X-axis.
Further, the machine tools, in which the table side structure moves along the X-axis, are usually designed so that an operator normally stands at a position so that the direction in which the table side structure moves to the left for the operator is defined as the positive (+) direction of the X-axis. However, even in such a machine tool, the operator sometimes moves to a position opposite to the normal position in order to confirm for example the position relationship between the tool and the workpiece. In this case, the direction in which the table side structure moves to the right viewing from the operator is the positive (+) direction. Accordingly, the positive (+) direction of the structure changes depending on the standing point of an operator, and therefore an operator may mistakenly recognize the structure to be moved and the moving direction thereof when the operator operates a manual feeding, whereby the tool and the workpiece may interfere with each other.
In order to prevent this, various technologies have been developed. For example, Patent Literature 1 describes a manual feed control device for a lath configured to indicate the moving direction of a cutter holder of the lath by the graphics of the cutter holder and an arrow. Further, Patent Literature 2 describes a program displaying device configured to display a virtual coordinate system, set by the G code, such as G68, along with the machine coordinate. Furthermore, Patent Literature 3 describes a machine tool, allowing a normal linear operation, in which the tool and the workpiece are manually fed along the three orthogonal axes of the X-, Y- and Z-axes, an oblique operation in which the tool and the workpiece are manually fed along an oblique line which is not parallel to the X-, Y- and Z-axes, and an arcuate operation in which the tool and the workpiece are manually fed along an arc by moving two or three of the X-, Y- and Z-axes, wherein an operation diagram, illustrating the oblique operation selected according to the angle of a previously set oblique line and the moving direction thereof are displayed, when the oblique operation is selected.